1. Field of the Invention
The present invention relates generally to enclosures, and more specifically to molded enclosures that includes knockouts.
2. Discussion of the Related Art
Molded plastic enclosures for various devices often include predefined knockouts that can be removed to allow access into the enclosure. For example, knockouts are removed to gain access for installing conduit fittings or electrical wires. Typically, referring to FIGS. 1 and 2, a continuous, substantially V-shaped groove 104 extends around the periphery of the knockout 102 such that the knockout can be removed through the application of an impact force to the knockout. Additionally, as shown in FIGS. 3 and 4, smaller nested knockouts 106 can be formed within other knockouts, such as larger knockout 102.
Existing molded-in knockout designs present difficulties in the injection molding process. For example, since the thickness of the wall is substantially reduced at the V-shaped groove 104, the plastic material flow is restricted around the periphery of the knockout as it flows across the V-shaped groove making it difficult to fill the knockout plug (center) causing potential cosmetic and injection molding issues. Such plastic flow is even more restricted with nested knockout configurations, as the plastic must flow across multiple, continuous V-shaped grooves.
Furthermore, it can be difficult to remove molded-in knockouts in plastic enclosures. Often, the user will need to repeatedly strike a screwdriver (or other tool) with a hammer to try to remove a molded-in knockout. Since most plastic enclosures have molded-in knockouts that have a smooth continuous surface, the screwdriver tip (or other tool) can easily slide across the face of the knockout making the removal much more difficult and increasing the chance of damage to the enclosure or injury to the user. This problem is worsened with nested knockout configurations, where it is difficult for the user to remove only one of the interior knockouts without damaging, partially removing or completely removing the adjacent outer knockout. Alternatively, the user may remove the knockout by striking a screwdriver placed in the V-shaped groove at multiple locations; however, such approach requires multiple hits and may damage the enclosure.
Several solutions have been presented to provide improved enclosure knockouts. For example, U.S. Pat. No. 5,444,183, which is incorporated herein by reference, provides flow leaders across grooves that better allow material flow to the interior knockouts sections during the molding process. U.S. Pat. No. 6,242,697, which is incorporated herein by reference, provides grooves that form concentric circular nested knockouts, the smaller diameter knockouts having sharper edges and deeper grooves than larger diameter knockouts to improve knockout removal. U.S. Pat. No. 6,765,147, which is incorporated herein by reference, provides a knockout that includes a tool receptor to receive a tool and upon a twisting of the tool, the knockout is removed without applying an impact force; thus, preventing damage to any electronics components behind the knockout.